iosiphonestoragewifi
I see there have recently been several products released that offer to give an iOS device access to local mass storage on the order of terabytes via WiFi. It appears that most if not all of these devices only allow access to the drive through a special (and very limited) iOS app for THAT product.
Via jailbreaking or otherwise, is there a way to use ANY iOS app (for example, photo, audio, and video editing apps) with local Wifi-connected storage?
CalDAV and CardDAV should definitely be two-way on iOS 4. I'm doing CalDAV right now through Google and I can confirm it works fine. I haven't tried CardDAV, but I haven't heard of any other issues. It's possible that your CalDAV server isn't set up properly, or you "Subscribed" to the CalDAV server instead of adding an account. Hard to say without knowing the particulars of your setup.
To add a CalDAV account:
You should be all set. If it doesn't work, check out things server-side.
Unfortunately not because there is no public API making these settings available to developers.
Best Answer
No, it is not possible in iOS and I'll bet it won't be implemented in near future. To be this feature possible, you need at least very fast wifi everywhere.